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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Photolithography Patterning of Complementary Organic Circuits

Ismail, Ahmad G. 20 April 2011 (has links)
The application of organic electronics to display technologies, large area electronic paper (or plastics), organic light emitting diodes (OLEDs), organic solar cells, radio frequency identification tags, smart cards and chemical sensors has received a great deal of attention in recent years. The main advantages of using organic semiconductors (OSCs) are lowcost, low processing temperature, flexibility, light weight and rugged design. The substantial progress in this field has been driven not just by existing technologies, such as flat panel displays, but also by new applications, such as flexible solid-state lighting, lowcost printed integrated circuits, and plastic solar cells, to name a few. Performance-wise, organic thin-film transistors (OTFTs) are on par with their a-Si (amorphous silicon) counterparts. Since OTFT fabrication offers lower processing temperatures and lower cost, it has the potential to replace a-Si in the near future. To date, all organic complementary circuits have used stencil mask patterning. Stencil mask patterning is not practical for mass manufacturing; hence, a way to pattern organic complementary metal-oxide-semiconductor (O-CMOS) using photolithography is paramount. This is the goal of this thesis. In this dissertation the design and fabrication of improved OTFTs for electronic displays and complementary circuits are illustrated. Here, we demonstrated OTFTs that have excellent stability; hence, they are more suitable for the above-mentioned electronic applications. In addition, for the first time, successful photolithographic patterning of an n-channel organic semiconductor is demonstrated. These important results have enabled us to integrate the n-channel and p-channel organic materials using a complete photolithographic process in realizing O-CMOS.
2

New conjugated polymers for organic electronics : synthesis, properties, and applications /

Zhu, Yan, January 2006 (has links)
Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 256-264).
3

Design and use of surface modifiers as tools for understanding and controlling interfaces in organic electronics

Smith, O'neil Lohanica 22 May 2014 (has links)
This thesis focuses on the use of surface modifiers as tools for probing and/or controlling interfaces. Surface modification of transparent conducting oxides (TCOs) with organic and organometallic modifiers can be used as a tool for mediating interfacial energetics as well as probing the kinetics of charge-transfer at the metal oxide/organic interface. The synthetic tunability of these modifiers allows us to design molecules based on various parameters, which include the nature of the binding, spacer, and terminal groups. Based on this framework, several modifiers were synthesized and used to investigate surface energy tuning as well as charge injection kinetics as a function of molecular structure. More specifically, we use XPS/UPS to examine the evolution of the chemical structure and frontier orbital levels of the TCO/organic interface as a function of the chosen surface modifier. In addition, we investigate the impact that various molecular binding groups have on mediating the kinetics of charge-transfer. In the last section of this body of work we examine the development of dielectric nanocomposite films for capacitor applications. More specifically, we examine the use of phosphonic acid modifiers to functionalize barium titanate nanoparticles in order to provide miscibility with a suitable polymer host. The effect of various modifiers on the dielectric properties not nanocomposite thin films was examined.
4

Heteroatom Substitution within Indenofluorenes

Marshall, Jonathan 27 October 2016 (has links)
The inclusion of atoms other than carbon into the framework of polycyclic conjugated hydrocarbons can have profound effects on the properties of the resultant compounds. Substitution of acenes with nitrogen-, oxygen-, and sulfur-containing rings has long been used as a strategy to alter the HOMO and LUMO energy levels of a compound and direct the solid-state morphology. In this thesis, I present my work in extending heteroatom substitution into the class of compounds known as indenofluorenes. Chapter I serves as an overview of indenofluorenes and related compounds with a special focus on the redox properties of these materials. Chapter II covers the synthesis and characterization of two selenophene-containing indenofluorene analogues. Chapter III discloses a new synthetic method for the preparation of unsymmetrical indenofluorenes and discusses the unusual reactivity of the dione precursors. Chapter IV is a comprehensive study of indacenodibenzothiophenes. This chapter investigates how heteroatom substitution affects the antiaromaticity of the indacene core and presents a detailed optoelectronic, computational, solid-state and materials study of a series of indacenodibenzothiophene derivatives. Chapter V presents my work towards the synthesis of the final unknown indenofluorene isomer, indeno[1,2-a]fluorene. Appendices A and B discuss my work done as part of Professor Shih-Yuan Liu’s research group at the start of my graduate career. This dissertation includes previously published and unpublished coauthored material. / 10000-01-01
5

Supramolecular scaffolding at the nanoscale : functional architectures as a step towards organic electronics / Plates-formes supramoléculaires à l'échelle nanométrique : architectures fonctionnelles comme une étape vers l'électronique organique

Cadeddu, Andrea 17 December 2012 (has links)
L’obtention d'un contrôle précis sur l'interaction entre les distinctes interactions faibles parmi les blocs de construction moléculaires à travers un design supramoléculaire permet la production de nanomatériaux auto-assemblées. Il s'agit de l’accès des chimistes « bottom-up» en matière de nanoscience et nanotechnologie. L'expansion d'une telle stratégie à partir de tectons bien définis fournit des solutions en vue de la fabrication de nanoarchitectures 1D, 2D et 3D avec des propriétés ajustables à volonté. Bien que l'utilisation des forces faibles à contrôler l'auto-assemblage aie déjà attiré une grande attention, nombreux sont les défis qui restent ouverts dans ce domaine. Entre autres, nous avons concentré notre attention dans le cadre de cette thèse sur trois aspects principaux:
- Le contrôle de l'auto-assemblage 2D, surtout orienté vers l’obtention d'un contrôle subtil du positionnement des unités fonctionnelles et de leur organisation, soit par rapport à le substrat, ou à les distances relatives et orientations des blocs de construction.
- Élargissement de l’ auto-assemblage 2D à la troisième dimension, c'est à dire la construction d’une architecture programmée, couche par couche, d'une façon rigidement contrôlée;
- Réactivité à la surface, qui, en dehors de l’attrait d’un point de vue industriel dans le développement de nouveaux catalyseur plus efficace, peut ouvrir la voie vers la synthèse de polymères conjugués 2D.
Trois thèmes complémentaires, constituant l'épine dorsale de ce travail de thèse, ont été traités par la combinaison de différentes méthodes physico-chimiques, incluant la microscopie à effet tunnel, la modélisation moléculaire, de relayer sur le développement instrumental et le logiciel, respectivement. La microscopie à effet tunnel est un outil puissant d’observation des phénomènes nanométriques alors que par le biais de simulations il serait possible de parvenir à une compréhension précise et de définir les principes de conception. Le premier objectif de ce travail de thèse a été la réalisation d'un contrôle sur les forces qui régissent l’auto-assemblage bi-dimensionnel de différents éléments constitutifs; Différents systèmes ont donc été considérés, allant de synthons disponibles dans le commerce, à de rares blocs de construction personnalisés. La microscopie à effet tunnel a été utilisé pour explorer l'auto-assemblage de la première génération de dendrimères sur graphite à l'interface solide-liquide, offrant un aperçu direct sur l'effet sur les interactions supramoléculaires. Une attention particulière a également été accordée à l'étude de la concurrence entre les différents adsorbats - un polyol aromatique et une bipyridyn-pyrimidin-amine, et à la modification des motifs d’emballage lors de l'addition de sels de différents métaux, in situ, comme dans le cas d'un tecton porphyrinique fonctionnalisé. En s'appuyant sur une telle connaissance de l'auto-assemblage 2D, nous avons étendu l'ordre à l'interface solide-liquide à la troisième dimension. Cela a été accompli en concevant un bloc hétéro-aromatique tétracarboxylique acide qui est capable de former une structure bi-couches autodirigée. [...] / Achieving a subtle control over the interplay between various distinct weak interactions between molecular building blocks through a supramolecular design makes it possible the production of self-assembled nanomaterials. This is the chemists “bottom-up” approach to nanoscience and nanotechnology. Such a strategy when applied on programmed tectons provides access towards the fabrication of 1D, 2D and 3D nanoarchitectures with properties at will. Although the use of weak forces to control self-assembly attracted already a great attention1, many are the challenges which are still open in the field. In the framework of this thesis we have focused our attention to three main aspects: Control over 2D self-assembly, especially addressed to achieving a subtle control over the positioning of functional units and their organization, either with respect the substrate, or with respect to neighboring molecules.Expanding the 2D self-assembly to the third dimension, i.e. growing programmed architectures, layer by layer, in a rigidly restrained fashion; Reactivity on the surface, which besides the industrial appeal in the development of new more efficient catalyst, may pave the road towards the synthesis of 2D-conjugated thus (semi)conducting polymers as synthetic graphene-like alternatives. Three complementary topics, constituting the backbone of this thesis work, have been addressed by combining different physico-chemical methods including Scanning Tunneling Microscopy (STM), Molecular modeling relaying on instrumental and software development, respectively. Scanning tunneling Microscopy is a powerful tool to monitor nanoscale phenomena whereas through Simulations one could attain a precise understanding and define design principles.The first objective of this thesis work was to achieve a control over the forces governing the bi-dimensional self-assembly of different building blocks at surfaces and interfaces. To this end, different systems were considered, ranging from commercially available synthons, to most rare custom made building blocks. STM was employed to explore the self-assembly of the first generation of dendrimers on graphite at the solid-liquid interface2, providing direct insight into the effect on the supramolecular interactions. Particular attention was also paid to the study of the competition between different adsorbates – an aromatic polyol and a bypiridyn-pirimidin-amine, and to the modification of packing patterns upon addition of different metal salts, in-situ, as in the case of a functionalized porphyrinic tecton . Building up on such a knowledge on 2D self-assembly, we have extended to order at the solid-liquid interface to the third dimension. This was accomplished by designing and investigating a hetero-aromatic tetracarboxylic acid building block which was found to form a self-templated bi-layered structure3. The unique design principle relies on the presence of four carbonyl moieties inside the conjugated core which we were found playing different roles: (i) they represent ‘‘primary’’ recognition sites on the molecular building blocks, to promote the self-assembly into 2D porous layers, (ii) they offer a fine control of their conformational planarity, which confers the self- templating capacity, and (iii) they introduce secondary recognition sites, which mediate the interactions between the self- assembled layers. The capacity of forming 2D supramolecular architectures is a prerequisite towards their use for exploring surface reactions, thereby forming frameworks, where the weak forces responsible for the self-assembly are substituted with covalent bonds or strong metallo-ligand links, aiming to obtain infinite two dimensional conjugate network, which will likely cover a key role in the next generation of electronic materials.[...]
6

Electrical switching and memory behaviors in organic-based devices

Tu, Chia-Hsun, 1973- 07 September 2012 (has links)
There is a strong desire to develop new, advanced materials that can overcome the scaling difficulties present in current memory devices. Organic materials are promising candidates for resistive switching memory devices due to their low-cost advantage, simplified manufacturing process, compatibility with flexible electronic devices, and ease of being constructed cross-point cell array architecture. The operation of these types of devices requires change of device resistance when subjected to an electrical bias. We study three different systems that can achieve this requirement, wherein one is believed to be related to the charge storage in metallic trapping site, inducing space-charge field, inhibiting the charge injection; another exhibits negative differential resistance (NDR) characteristics; and the electrical transition of the third one is believed to be attributed to the formation of filaments. / text
7

Stacked inverted top-emitting white organic light-emitting diodes

Najafabadi, Ehsan 12 January 2015 (has links)
The majority of research on Organic Light-Emitting Diodes (OLEDs) has focused on a top-cathode, conventional bottom-emitting architecture. Yet bottom-cathode, inverted top-emitting OLEDs offer some advantages from an applications point of view. In this thesis, the development of high performance green electroluminescent inverted top-emitting diodes is first presented. The challenges in producing an inverted structure are discussed and the advantages of high efficiency inverted top-emitting OLEDs are provided. Next, the transition to a stacked architecture with separate orange and blue emitting layers is demonstrated, allowing for white emission. The pros and cons of the existing device structure is described, with an eye to future developments and proposed follow-up research.
8

Electrical switching and memory behaviors in organic-based devices

Tu, Chia-Hsun, January 1900 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.
9

Transition Metal Oxides in Organic Electronics

Greiner, Mark 19 June 2014 (has links)
Transition metal oxide thin films are commonly used in organic electronics devices to improve charge-injection between electrodes and organic semiconductors. Some oxides are good hole-injectors, while others are good electron-injectors. Transition metal oxides are materials with many diverse properties. Many transition metals have more than one stable oxidation state and can form more than one oxide. Each oxide possesses its own unique properties. For example, transition metal oxide electronic band structures can range from insulating to conducting. They can exhibit a wide range of work functions. Some oxides are inert, while others are catalytically active. Such properties are affected by numerous factors, including cation oxidation state and multiple types of defects. Currently it is not fully understood which oxide properties are the most important to their performance in organic electronics. In the present thesis, photoemission spectroscopy is used to examine how changes in certain oxide properties–such as cation oxidation states and defects—are linked to the oxide properties that are relevant to organic electronics devices—such as an oxide’s work function and electron band structure. In order to unravel correlations between these properties, we controllably change one property and measure how it changes affects another property. By performing such tests on a wide range of diverse transition metal oxides, we can discern broadly-applicable relationships. We establish a relationship between cation oxidation state, work functions and valence band structures. We determine that an oxide’s electron chemical potential relative to an organic’s donor and acceptor levels governs energy-level alignment at oxide organic interfaces. We establish how interfacial reactivity at electrode/oxide interfaces dictates an oxide’s work function and electronic structure near the interface. iii These findings demonstrate some of the very interesting fundamental relationships that exist between chemical and electronic properties at interfaces. These findings should assist in the future development and understanding of the functional interfaces of organic semiconductors and transition-metal oxides.
10

Charge Injection and Transport in Pentacene Field-Effect Transistors

Masurkar, Amrita Vijay January 2017 (has links)
Since the seminal discovery of conductive polymers four decades ago, organic electronics has grown from an exploratory field to an industry offering novel consumer products. Research has led to the synthesis of new organic molecules and polymers and their applications: organic field-effect transistors (OFETs), organic light-emitting diodes, and organic photovoltaics. The goal for research as well as for industry is producing low-cost, flexible, and, ultimately, sustainable, electronics. Although on the rise, organic electronics faces several challenges: air instability, reliability, and scaling, to name a few. And despite that organic devices and larger systems have been demonstrated, there remains a gap in understanding underlying mechanisms behind light absorption, photoconduction, charge transport and conduction in them. The primary purpose of this thesis is to use a relatively under utilized technique, photocurrent microscopy (PCM), to directly probe charge carriers in pentacene and 6,13-Bis(triisopropylsilylethynyl) (TIPS) pentacene FETs to learn about charge injection and transport. The latter part of the thesis focuses on the use of thiols to modify electrode properties to both increase charge injection efficiency and to provide passivation to low-work function metal electrodes. It is demonstrated for the first time experimentally by directly probing the OFET channel that top-contact geometry OFETs suffer minimally from a charge injection barrier, and that trap filling and altering of trap density-of-states in the channel is directly observable with PCM. PCM was used to investigate grains and grain boundaries in TIPS-pentacene devices. By varying gate bias, it was shown that the PCM maps of grains are not simply a result of varying absorption on the surface of the film; rather, it is an artefact of charge transport between grains and grain boundaries. Through this study, PCM was shown to be a useful, large-area scanning technique, for observing transport in devices with large (on the order of 50 $\mu$m) grains. This is particularly relevant as solution-proccessable films are likely to dominate the flexible electronics industry. The thiol portion of this thesis compares the impact of two distinct thiols on bottom-contact pentacene FETs: perfluorodecanethiol (PFDT) and pentafluorobenzenethiol (PFBT). Using X-ray photoelectron spectroscopy to measure metal oxidation, it was determined that short aromatic thiols are poor choices for low work-function metal passivation. In addition, both passivation and charge injection enhancement can be achieved with long fluorinated alkanethiols. However, there is a trade-off between passivation and on-current. The enhancement of on-current in thiol-treated Cu-electrode pentacene devices is most likely not morphology related, due to the fact that PFDT was found to be in a standing-up orientation on the metal surface. Additionally, it was demonstrated that although highly electronegative atoms such as fluorine can beneficially modify metal work function, too many fluorine atoms in thiols can lead to too high a work function and a large mismatch between the pentacene highest-occupied-molecular-level and metal work function.

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